DVD is an abbreviation of Digital Versatile Disc, the successor to the Compact Disc (CD).
In a nutshell, a 120 mm DVD can store at least 4.3 GiB worth of data, which is far greater than what a 120 mm CD can (up to 0.8 GiB if you're lucky).
DVD's birth process was not a painless one, quite unlike CD's, because there are several companies/groups each pushing their competing technology with obvious vested interests.
Similar to CDs, DVD also comes in recordable (and rewritable) varieties. Unfortunately, there are competing standards for DVD recordable technologies; most modern DVD drives, however, should be able to read these different technologies without much problem.
Future of DVD
Like its conception, DVD's successor also shows signs of fracture, with competing standards such as HD-DVD, BluRay, and HVD.